For the manufacture of injection molded articles and in particular when using hot runner nozzles for the manufacture of moldable articles, the temperature of the molten material on its way through a manifold, hot runner nozzles, and within the cavity is crucial for the later quality of the article in the same cavity, between cavities, during the same injection cycle and also between subsequent injection cycles. There have been made great efforts to control the temperature of all the components that guide the molten material to the cavity but these efforts did not yet resolve critical issues for hot runner nozzles.
In the first known design shown in FIG. 9 a single mold cavity has a single mold gate and molten material is injected via a single nozzle tip. The nozzle tip belongs to a hot runner nozzle that can have either a single tip or at least two nozzle tips. In these designs, the flow of molten material inside the mold cavity is split around and behind the mold core into two streams of molten material. The flow of these two streams of molten material in the cavity is affected by the presence of a thin frozen molded material layer that starts in the vicinity of the gate and can be formed not only on the cold walls of the cavity but also around the cold mold core. These frozen layers impact the feeling of the cavity and the quality of the part. Also a weld line will be formed behind the mold core when the two split streams of the molten material meet. The weld line could be visible or could weaken a molded part. Such weld lines are thus not desirable.
In the second known design, shown in FIG. 10, a single mold cavity has at least two mold gates and molten material is injected via two separate nozzles and two separate nozzle tips directly onto and around a mold core. In these designs there are two flow streams of molten material inside the mold cavity around the mold core. These streams are affected by the presence of a thin frozen molded material layer that starts in the vicinity of the gate and can be formed not only on the cold walls of the cavity but also around the cold mold core. These frozen layers impact the feeling of the cavity and the quality of the part. In these designs a flow line will likely happen when the two streams meet in the cavity. The weld line could be visible or could weaken a molded part. Such weld lines are thus not desirable.
Therefore there is a need met by this invention to extend the control of the temperature of the molten material and/or of the components guiding the molten material also to the cavity for an improvement of the quality of the molded articles.